In a process of manufacturing, for example, a semiconductor device, a liquid crystal panel and the like, various processes such as a film forming process, an etching process, an oxidation process and the like are performed with respect to an target object such as a semiconductor substrate or a substrate for liquid crystal (hereinafter, the semiconductor substrate or the substrate for liquid crystal is simply referred to as a “wafer”) inside individual processing containers. In general, when the target object is loaded into and unloaded from the processing containers, a transfer device equipped with a holding part for holding the target object is used. Among various types of transfer devices, a transfer device which reciprocates a holding part by expanding or contracting a single-joint arm or a multi-joint arm is widely used.
In order to align and load the target object at a desired location inside the processing container using the transfer device equipped with the holding part, various alignment technologies have been devised. As an example, a technology for obtaining the central position of a semiconductor wafer and mounting the semiconductor wafer on a predetermined location of a mounting table is known. This technology uses two sensors to always accurately obtain the center of the wafer, thereby enhancing the accuracy of obtaining the center.
However, this technology does not disclose a misalignment involved in a thermal expansion of a transfer arm which supports the holding part for holding the wafer, a correction technique used to address such misalignment, and the like. In general, when various processes such as a film forming process or an etching process are performed with respect to a target object such as a semiconductor substrate, the interior of a processing container is kept under a high temperature condition of, e.g., 700 degrees C. In addition, the processing container and the like are not always kept at a constant temperature, but a temperature may be elevated and varied with time in parallel with the initiation of processing.
The transfer arm which supports the holding part for holding the wafer undergoes a time-dependent change in temperature or is exposed to a high temperature environment. As such, the transfer arm repeatedly undergoes thermal expansion or contraction. Thus, when mounting a target object (object to be processed) within a processing container, there is a need to acquire correct position information of the transfer arm or the holding part according to a temperature state on each occasion, thereby performing alignment. In particular, the transfer arm is generally made of a material of aluminum from the viewpoint of lightening the weight or realizing versatility. Thus, a thermal expansion coefficient of the transfer arm is greater than that of the holding part made of SUS and the like. For this reason, it is important to consider elongation or deformation of the transfer arm in performing the alignment.
That is to say, a rate at which temperature is elevated or dropped within or near a processing container varies with time according to environment. As such, there is a concern that elongation or deformation involved in the environment is exerted on the transfer arm. Therefore, it is necessary to acquire as much position information of the transfer arm as possible, in the vicinity of the processing container and immediately before mounting the target object. In this regard, the conventional technology is designed to address such a requirement by detecting position information of a holding part as a target in the vicinity of an inlet of the processing container, at a time when the holding part is loaded into a processing container. However, the conventional technology does not detect or measure the position of a transfer arm in consideration of the shape of the transfer arm at a timing where a holding part enters a processing container (a state immediately before the transfer arm is fully expanded).